On 31/05/13 01:22, Mathias Burén wrote:
On 30 May 2013 22:23, Dominic Raferd <dominic@xxxxxxxxxxxxxxx> wrote:
I am wanting to (re)set up my raid1 array with 1 SSD partition (/dev/sda2)
and 1 'rust' drive partition (/dev/sdb1) , both 240GB. SSD will also have a
very small ext2 partition mounted as /mnt/sda1 (to hold the write-intent
bitmap file).
To get the full speed of the SSD for reads and to maximise speed for writes
I plan to use these settings:
mdadm -C /dev/md0 --level=raid1 -n 2 /dev/sda2 --write-mostly
--write-behind=16384 --bitmap=/mnt/sda1/write-intent-bitmap.file
--bitmap-chunk=256M dev/sdb1
Will this work and be optimal? I am not too bothered about the write-intent
bitmap file but it is not optional I think, hence I set a large chunk size,
could or should it be even larger (or smaller)? Similarly I have tried to
set a high write-behind to speed up writes as much as possible - is 16384
the maximum allowed?
My system has mdadm 3.2.3 and kernel 3.2.26.
Any suggestions gratefully received.
Dominic
Quick question: Why not a 2 drive "RAID10"?
Thanks for your reply Mathias. I am not familiar enough with RAID10 to
know if or how this would work, nor am I sure if it would work OK with
my OS (Devil-Linux), whereas I have used mdadm with RAID1 for many years
with conventional drives. My idea is to upgrade one of my existing
drives to SSD and to get all the read-speed advantages of SSD and as
much write-speed improvement as possible. If RAID10 can do this better
than RAID1 then please tell me more!
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